Vacuum tube circuits



' Sept-v2, 1930. v E. E. TURNER. JR 1,775,073

VACUU TUBE CIRCUITS rma June 2o, 1927 8 /2 E3 ZZ Z5 /3 2/ 1N VENTOR.

EDw//v E. Tue/75e Je.

Patented Sept. 2, 1930 ViuNrrED STATES PATENT 'or-*FICE EDWIN E. TUBNE, JR., OF WEST ROXBURY, MASSACHUSETTS, ASSIGNOR TO SUBMA- EINE SIGNAL COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MAINE.

VACUUM- TUBE CIRCUITS f Application led June '20,

The present invention relates to a sound receiving system particularly .adaptable for the taking of soundings by the measurement A of the time interval necessary for a sound l impulse to travel to the bottom and the re- 1@ tial delay and further that it be of sufiicient sensitivity and stability to warrant commercial adoption on vessels of all types.

ln the present invention `the impulse receive'd by the microphone receiver commences the operation of a certain transient phenomenon which has a reactive effect, building the phenomenon up so rapidly' as to cause a powerful induced voltage across a suitable indicator. ln one form of the system em ployed after `the phenomenon has built up to a maximum the circuit remains paralyzed until manually released, but in the preferred form, which I employ, normal conditions are again established Within a comparatively short time so that the circuit is again ready to receive a succeeding impulse.

As the speed of sound in wateris approxi.- mately'four times asfast as in air, and as the intervals to be measured in the systems where the present invention is employed are often as small as one hundredth o a second,

. it can readily be appreciated that an errorv of 10% only allows a time interval error of one thousandth of va second and-, tlierefore,v that the apparatus must operate not only ex:

tremely accurately but quickly. y

For this reason I have made use of the transient phenomenon of a circuit whose time constant is of a smaller 'and different order 40 of magnitude than t'he time interval to be of the apparatus. has it been possible to eliminate Not onl. 'all mechanical relay or current controlling devices, butit has also been possible to design a current controlling device which will operate on aminimum intensity ofV signal.

1927. semi No. 200,056.

The latter fact makes it possible to measure depth with far greater accuracy over a much larger range than heretofore.

The mechanical relays formerly employed in inding depths of water by the so called time of travel method are not particularly stable, since they are usually operated on small current and control currents of considerable value. Difficulty has further been found in eliminating external vibrations, which usually operate the relay, and also in keeping the relay in adjustment due tothe minute arcing which occursin breaking an electrical contact.

In the present electrical system', all these difficulties have been avoided. The signal is first received on a microphone, then passed through a filter to eliminate the extraneous sounds, and finally impressed upon the relay circuit. It isparticularly important to filter the extraneous sounds in the present case, since the relay circuit is aperio'dic and would operate on any impressed potential. This followsdirectly from the nature of the relay, since the latter operates by means of the transient phenomenon established in the circuit. and is independent of frequency, and since merely by impressing the minimum potentialy on Athe gridof the proper tube in the circuit, the relay-o erates regardless of the frequency of the po ential impressed. Itis, therefore, quite essential to eliminate any slg- Y nals or noises which are not desired in the relay circuit is kept within certain limiting v values regardless of the strength of the initial signal.' Inv this manner all diiliculties flue to shocksl in the system, paralyzi'ng the tubes,

v or excessive `potentials are eliminated and the.

circuit operates uniformly for any signal of vsufficient strength'to operate it.

The theory underlying the operation of the system, as well as the operation itself, will be best understood from the following description in connection with the drawings, in'which f Figure 1 shows the general circuit; Figure 2 shows the circuit with a slight modification; and y Figure 3 shows the circuit with still'another modification. I In Figure 1, the sound is received by the microphone or other sound receiver 1 which translates the sound impulse into electrical' .variations and impresses the latter upon the filter 2. The microphone is energized by a direct current source 5 by means of the potentiometer 4, which controls the amount of direct current Vpassing Ythrough the microphone.l A choke 3 is also provided to bypass the direct current and allow the current variations due tothe sound impulses to be impressed upon the filter circuit. From the output of the filter the impulses are delivered to the transformer 6; that is, the desired signal impulses, since the other electrical impulses are filtered out. The filter is constructed tol bypass current variations of the signal frequency, since the sound signal land therefore the electrical variations have the same well defined frequency. vIt is essential to have a signal of a Well defined frequency as theisound signal to be received, since the relay is designed to operate on any impulse and would, therefore, be operated by any im-` pulse if a filter were not provided to eliminate extraneous impulses and transmit a signal of a given frequency.

The vacuum tube 10 and its associated circuits act as an amplifier for the signal impressed upon it by the transformer 6 and conceivably could be omitted from the circuit provided the signal was of sufficient intensity. It is, however, advantageous to amplify after filtering, as usually the filtered signal is not' sufficiently powerful.` to operate the rest of the circuit in the manner desired.

The rest of the circuit comprises a detector tube 11 and its circuit, the function of which will be explained in greater detail later, the

relay control tube 12 and its circuit, the relay tube 13 together with its circuit, and the indicating tube and circuit.

The signal is impressed upon the detector tube circuit by the transformer 7, the primary `of which is connected to the output gif the prior tube circuit.l The detector tube and circuit operate in the usual manner and may employ a grid leak and condenser as shown in Figure 1 or a slight grid bias as shown in Figure 2, where the grid return' goes back to the negative side of the filament. In the circuit' shown both in Figure 1 and Figure 2, the detector tube rectifies the signal. In Figure 1, when a signal is impressed upon the tube 11, the plate current in the primary of the transformer 8 is decreased. 'The secondary of the transformer 8 is so" connected that the grid side of the secondary of the transformer becomes more positive. r1 he grid of the tube 12,.therefore,.greatly increases the at once.

flow of (plate currentl in the circuit of that y tube an through the primary. of the transformer 9. The terminals of the vsecondary of this transformer are so chosen that the rid of the tube 13 becomes negative, thus tenl ing to deg'ease the flow of electrons from the filament to the plate and therefore decreasing the venting a large plate current from flowing in the plate circuit` of that tube. in the resistance 16 decreases,.the potential of the point of connection of the lead 18 to the resistance 16 approaches the same potential as the point 24, since the potential drop between 24 and the leadv18 has de.-

creased.l Obviously', the grid of tube 12,

although negative with respect to the filament of the same tube, has become less negative, thus tending to further increase the plate current of the tube 12. This effect continues; namely, that of increasing the plate -current in the tube 12 and decreasing the plate current in thev tube 13 by making the grid of the tube 12 more and more positive with respect As the current lll) t the filament of the same tube, and making the grid of the tube 13 more negative by the rapid change induced from the primary of the transformer 9 to the secondary of the tube 13,

of which the negative end connects with the grid of the tube. It is possible that even after passing through the filter and rectifier the incoming signal may be so large as to overcome completely the negative bias on the grid tube 12 in which case the plate cur? rent of tube 13 will be considerably reduced However, it is not at all necessary that the si al current be so large and infpractice it willig much smaller than this.- The incoming signal need be only strong e'nfough to' cause somedecrease in the plate current of tube 13 after which, by the action just yexplained, the plate current will automatically be further reduced.

An important feature lof the operation of" the ciricuit is that the current in the rimary of the transformer'21, which-isin t e plate circuit of the tube 13, is made'to changeiat such a rapid rate by this transient henomenon which takes place. inthe circuitv that a high voltage is induced in'its windings and a .correspondingly much higher voltage across the' secondary, since the transformer is a. step up transformer, with the result that the gap in theindicator 20 is' broken down' momentarily and an electric discharge occurs across it, giving an indication.

Since the. grid of the tube 13 is connected through the secondary of the transformer'9 to the ositive end of the filament, as soon as the e ect of vthe transient phenomenon due to the signal has passed, it will assunf the potential of the positive side of the filament,

establish rapidly (but not so rapidly as the breakdown occurred as is explained below, since thereby another flashwould be produced) the normal current flowing in the filament plate circuit of the tube 13 and be ready again for another signal.

It will be noted that the above'operation is notin the ordinary nature of a feed back or a regenerative efiect, since there is no tendency i towards the buildin up of sustained oscillation or any repeate steady state reaction in the circuitsinvolved. The portions of the complete circuit are so intimately connected'` with one another that the breakdown of the v current in the last tube occurs from the simultaneous chan e in the Whole system and not on account any feed back from one part of the system to another. Y

To give an explanation of the above statement, it will be noted that simultaneous with the potential of the grid of the tube 13 becoming more negative, the current in the resistance 16 drops and the grid of the tube 12 ,v becomes more positive with respect to the filament of that tube, and, therefore, the grid of the tube 12 isfurther changed positive even as the current in the filament plate circuit of tube 13 is decreasing.

It may further be noted that the control of the' potential of the grid of the tube 12 is positive, controlled by the position of the lead 18 on the resistance 16 and that the potential ofthe grid of the tube 13 is controlled indirectly therethrough by the resulting potential induced across the secondary of the transformer 9, which potential overcomes the normal potential of the grid above the filament, since vthe former is connected to the positive side of the hiatnent.' ,f

rlhe circuit is urposely designed so that the'brealzdown o? the plate-filament current in the tube 13 occurs very rapidly and the building up to a normal value afterthe breakdown takes place much more slowly, so that the indicator 20 will not discharge twice, once on the breakdown and once on the building up. Further, the method employed in the present case is that of causing the indication c by the interruption of an established current rather than by establishing a current. i The former method has been ound to be more sensitive, reliable and capable of giving bet- "ter indications.,

v The circuit employed in Figure 2 is sometimes preferable to that in Figure 1, since it includes a, means for limiting the signal strengthfinally inducedy into the circuits of eter 24 so that its potential may be adJusted with respect to the the last twg tubes. Whereas in Figure 1 av the position of the lead 17- With'respect to the battery 14, in the circuit shown in Figure 2 the plate potential of the tube 1l goes to thepotentiometer 24 across the filament battery 15 and thereby allows a smaller and better adjustable method of giving the correct potential to the'plate of the detector tube. The grid return ofthe detector tube l1 in Figure 2 returns to the negative side of the filament. The result of this arrangement ofthe circuit shown in Figure 1 is that the detector tube is operating on the lower part of the plate fila-` ment characteristic Where th@ preponderance of change by rectification causes an increase in plate filament current, since a small positive change in the potential of the grid causes a correspondingly large increase inthe plate filament current, whereas a small ne ative change in the potential of the grid hard y decreases the plate filament current.

' The plate return 17 is led to the potentiomosit'ion and thereby its filament'and that thereby the plate filament current may be controlled.V Thus it is possible to limit the maximum response of the detector tube Without substantially affecting lits sensitivity to weak signals, as the effect Aof increasing the potential of the plate With v limiting maximum plate filament current below the value of possible harm or undesirability is essential to the good operation of the circuit.

rlhe operation of the detector tube in Figure' 1 with a grid leak and condenser-is such as to cause a building up of a negative potential on the grid of the detector tube with respect toits lament and therefore cause a decrease in the plate filamentcurrent. @n receipt of the signal in the detector tube the plate current in the transformer 8 of Figure 1 decreases, which is the opposite condition from that which ha pens in the circuit of Figure 2. llt is evidyent, therefore, since in the present invention it is highly essential to havethe'grid of the tube 12 go positive, that the secondary ofthe transformer 8 must have reversed positions in Figure 1 from that in Figure 2 in order to obtain the correct potential on the grid of the tube 12.

The circuit shown in Figure 3 differs from that in Figure 1 in that the grid of the tube 13 is made to go negative bymeans of the resistance 22 in place of the transformer@ i shown in Figure 1. When the grid of tube 12 becomes more positive than initially on account of the signal, the current in the plate filament circuit increases, and, therefore, the potential difference across the resistance 22.

Since the current flows in the directionof diers from the operation of Figure '1 in that.

in order to restore the grid to its normal potentiavl the key must be closed, whereas in Figure 1 after the change has occurred the grid assumes its normal potential, that ofl has been explained, is designed to operate 'the positive side of the filament. 2f)

.the circuit by making the grid of' the last While I wish to make it clear that I prefer to operate tube negative .and interrupting la current already established, it is also possible to operate the circuit in the reverse manner by causing the grid of thetube 12 to become negative and that of tube 13 positive and bring about the rapid establishment of the plate filament current in the last tube. The indicator, as

on a change of current and itmakes no difference, therefore,`1nwhat directlon this change occurs.

As has been mentioned labove, the re-v establishment of normal conditions is brought about after the chann'e has died down and no current is fiowing in the plate filament i circuit of the last tube by the fact that the grid return is connected to the positive side of the filament, therefore giving the grid a slight positive charge over thefilament.`

Since this is a constant positive potential and is not amplified by any interaction be tween tubes and circuits as the breakdown is, the normal plate filament current in the last tube builds up more slowly than the break' down, so that the potential induced across the indicator' is not enough tooperate it, even `though the current in the circuit is brought However long the.

back to its normal value. time for the restoration of normal pla'te filament current is, it is never of such a'time interval as to prevent a very rapid operation of the device. The' restoration is less than one thousandth of a. second, how much is difficult to say, and the occurrence of the operi ating phenomenon is, of course, much less than that.

Having described my invention, I claim: 1. In a system for indicat-ing the reception of wave energy, a plurality of vacuum tubes and vacuum tube circuits comprising a de'- tector tube and detector tube circuit, a second vacuum tube and vacuum tube circuit coupled Y to the output of said detectortube circuit, and

a third vacuum tube and vacuum tube circuit 'coupled to the output of said-second vacuum respect to its filament, and a resistance common in part in the plate filament circuit 'of both said second and third circuits for further increasing the positive potential bf the grid f said secondV tube with respect to said filament.

2. In a system for indicating the reception ofl wave energy comprising a plurality of vacuum tubes and circuits, including means for impressing a positive potential upon the grid of one tube, means controlled by the operation of the -first named means for impressing a negative potential upon the grid of a second tube, and means common inthe plate filamentvcircuit of the circuits of both tubes for further increasing the positive potential upon the grid of the first tube.

In a system for bringing; about the operation of an indicator by the rapid change in the plate filament current of a Vacuum tube circuit comprising a three element vac* uum tube having a'comparatively large plate filament current, a second three element vacuum tube having a negligible-plate filament current and means including the above recited elements for increasing the plate filament current of the second vacuum tubeand decreasing theplate filament current of the first lvacuum tube, the decrease being of a larger order of magnitude than the increase.

4. In a system for bringing about the op eration of an indicator by the rapid change in the plate filament current of a vacuum tube comprising a plurality of vacuum tubes and circuits having. partly in common in the plate filament circuits resistance means and separate connecting points on said resistance for thefilament and grid of one'of said tubes, and means including said tubes and circuits for increasing the plate filament current in said lastA mentioned tube and decreasing the same in the following tube, said decrease being of a substantially larger order of magnitude than said increase.

5. In a system for bringing about the operation ot an indicator by the rapid change in the plate filament current of a Vacuum tube comprising a plurality of vacuum tubes' and circuits having partly in common 'in 'the plate filament circuits resistance` means and separate connecting points on said resistance means for the filament and grid of one of saidtubes, and means including said tubes and circuits for increasing the plate filament current 'in oney tube and decreasing the same in another tube, the change in one beingof a different order of magnitude from the other.

6. In a system for bringing about the opsaid second coupling being arranged to make .the grid of said third tube negative with eration of an indicator. by the rapid change in the plate filament current of a vacuum tube tubes and circuits for increasing the plate.

filament circuit in one tube and decreasing the same in another tube, the change in one beingfof a different order of magnitude from the other.

7. In a system for bringing about the operation of an indicator by the rapid change in the plate filament current of a vacuum tube comprising a plurality of vacuum tubes and circuits connected in cascade, means included in the plate filamentvcireuits of said .tubes having different potential connecting points for the filament and grid of one of said tubes, /means for impressing a potential in a chosen direction upon the grid of one of said tubes andimeans for impressing aI potential in the opposite direction on the grid of the following tube, said action changing rapidly 'the plate filament current in said first mentioned tube and bringing about further potential changes with respect to said potential connecting points whereby the action becomes cumulative.

8. In a system for bringing about the oper- -ation of an indicatorby a rapid change in the plate filament current of a vacuum tube comprisingr means for impressing a potential change in a chosen direction upon the grid of one vacuum tube and means for impressing a potential change in the opposite direction upon the grid of a following tube, thereby changing the plate filament current in the latter tube, and means operated by the change in said plate filament current for impressing a further potential change in the said chosen direction upon the grid of the first vacuum tube, whereby a complete change of the plate filament current in the last tube pioduces a cumulative effect.

9. In a system for bringing about the operation of an indicator by a rapid change in the plate filament current of a vacuum tube comprising means for impressing a potential -changein a chosen direction upon the grid of one vacuum tube and means for impressing a potential ,change in the opposite direction upon the grid of a following tube, thereby changing the plate filament current in the latter tube, means operated by the change in said plate filament current for impressing a further potential change in the said chosen y direction upon the grid of the first Vacuum tube, whereby a complete change of the plate filament current in the last tube produces a cumulative effect, and means operated by the rapid change in said current. for causing an indication.

l0.` In a system for' bringing about the opcomprising means for impressing a potential change in a chosen direction upon the grid of one vacuum tube and means for impressing a potential change in the opposite direc- .tion upon the grid of a following tube, thereby changing the plate filament current in the lattertube, means operated by the change in said plaie filament current for impressing a further.potential changein the said chosen direction upon the grid of the first vacuum tube, whereby a complete change of the plate filament current in the last tube produces a cumulative effect, and an indicator operated by the voltage induced from the rapid current change.

11. Iii a system foi-.indicatingthe reception of Wave energy. a detector circuit, an electron tube relay circuit adapted to cause a rapid changeiii current in an indicating circuit upon the reception of wave energy, and means included in the detector circuit for adjusting the maximum amplitude of the impressed impulse, whereby the electron tube relay circuit is spared of any Lndesired effect.

l2. ln Aa system. for indicating the reception of wave energy.`an electron tube relay by means of the transient change in current iii the plate filament circuit of a vacuum tube, Ineans operated through an initial electric impulse for inducing-a potential upon the grid of said Vacuum tube in 4vthe direction opposite to the normally impressed potential with respect to the filament of the same tube and thereby commencing the change in said plate filament current, means operated by said change for rapidly increasing said change and means for more slowlyv reestablishiiig normal conditions after said change is over, whereby the restoration of conditions' will not cause the operation-of the indicator.

14. A system for indicating the reception of a sound signal substantially simultaneously with its reception comprising a sound receiver ffor receiving the sound and converting the same to corresponding electric variations, a filter operatively connected to said receiver for eliminating other than the signal desired to be received, indicating means and means operatively connecting said filter to said indicating means including a vacuum tube and circuit having normally a uniform for 7rapidly-increasing the negative potential on the grid of said tube comprising a vacuum tube and circuit connected to the input of' said first mentioned tube and a resistance connected in common in both filament plate circuits of both tubes for impressing the negative drop as a transient phenomenon on the first mentioned tube. l

15. A systemfor indicating the reception of a sound signal substantially simultaneously vwith its reception comprising a sound receiver for receiving the sound and converting the same to corresponding electric variations,

a filter operatively connected to said receiver v for eliminating other than the'signal desired to be received, electric discharge indicator and means operatively connecting said filter to said electric discharge indicator including 'a vacuum tube and circuit having normally a uniform plate filament current and means for rapidly decreasing said plate current including means for rapidly increasing the negative potential on the grid of said tube comprising a vacuum tube and circuit connected 4to the input of said first mentioned tube and a resistance'connected in common in beth filament plate circuits of both-tubes for impressing the negative drop as a transient phenomenon on the first mentioned tube.

16. 'In a system for indicating thereception of wave energy, an electrontube relay circuit including means for causing a collapse of the plate current in said circuit in resl onse to an impressed signal, a detector circult for impressing a signal potential in a definite d-irection upon the electron tube circuit, and means included in the latter circuit for effect- 'ing a restoration of the normal plate current in thecircuit after the reception of the Wave' energy.

Intestimony whereof v I afiix my signature,

' EDWIN E. TURNER, JR; 

